This is something I've been wondering about for quite some time, particularly given that large providers can hash the images and conserve storage space by stori

This is something I've been wondering about for quite some time, particularly given that large providers can hash the images and conserve storage space by storing only a single copy of the image per hash. I would suspect there are privacy implications of google caching what's behind every image tag in an email, in addition to the massive traffic / CPU spike such a thing might cause to retrieve the image and hash it, particularly for a very large email campaign. (But I don't know). [Edited to include this link, which I found in another comment here] "Gmail will now serve all images through Google’s own secure proxy servers." https://gmail.googleblog.com/2013/12/images-now-showing.html https://gmail.googleblog.com/2013/12/images-now-showing.html